Lexus NX manuals

Lexus NX: Check Bus 3 Line for Short to +B

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Check Bus 3 Line for Short to +B

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and +B when there is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.

Symptom

Trouble Area
*1: w/ Telematics Transceiver

*2: w/ Bus Buffer ECU
  • There is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.
  • There is no resistance between terminal 19 (CAYH) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 20 (CAYL) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.
  • Short to +B in CAN main bus wire
  • Short to +B in CAN branch wire
  • Central gateway ECU (network gateway ECU)
  • DCM (telematics transceiver)*1
  • Bus buffer ECU*2
  • Radio receiver assembly
  • No. 10 CAN junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

NOTICE:

  • Before measuring the resistance of the CAN bus, turn the power switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal.

    Click here

  • When disconnecting and reconnecting the auxiliary battery.

    Click here

    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

    Click here

  • Some parts must be initialized and set when replacing or removing and installing parts.

    Click here

  • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.

    Click here

  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

    DTC check procedure: Turn the power switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.

  • After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.

    Click here

  • The following malfunctions may occur if a radio receiver assembly from another vehicle is installed to this vehicle. Therefore, when replacing the radio receiver assembly, be sure to replace it with new one.
    • Communication malfunction DTC is output
    • Does not operate normally

HINT:

  • Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE

1.

CHECK FOR SHORT TO B+ IN CAN BUS WIRE (NO. 10 CAN JUNCTION CONNECTOR)

(a) Disconnect the cable to the negative (-) auxiliary battery terminal.

(b) Disconnect the No. 10 CAN junction connector.

*a

Front view of wire harness connector

(to No. 10 CAN Junction Connector)

*b

to Central Gateway ECU (Network Gateway ECU)

*c

to Radio Receiver Assembly

*d

to DCM (Telematics Transceiver) (w/ Telematics Transceiver)

*e

to Bus Buffer ECU (w/ Bus Buffer ECU)

*f

to Central Gateway ECU (Network Gateway ECU)

*g

Front view of DLC3

-

-

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

Connected to
*1: w/ Telematics Transceiver

*2: w/ Bus Buffer ECU

I164-1 (CANH) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

Central gateway ECU (network gateway ECU)

I164-12 (CANL) - I182-16 (BAT)

I164-2 (CANH) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

Radio receiver assembly

I164-13 (CANL) - I182-16 (BAT)

I164-3 (CANH) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

DCM (telematics transceiver)*1

I164-14 (CANL) - I182-16 (BAT)

I164-4 (CANH) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

Bus buffer ECU*2

I164-15 (CANL) - I182-16 (BAT)

I164-5 (CANH) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

Central gateway ECU (network gateway ECU)

I164-16 (CANL) - I182-16 (BAT)

Result

Proceed to

OK

A

NG (Central gateway ECU [network gateway ECU] CAN main wire)

B

NG (Wire to ECU or sensor)

C
A

REPLACE NO. 10 CAN JUNCTION CONNECTOR
C

GO TO STEP 4

B

2.

CONNECT CONNECTOR

(a) Reconnect the I164 No. 10 CAN junction connector.

NEXT

3.

CHECK FOR SHORT TO B+ IN CAN BUS WIRE (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 10 CAN JUNCTION CONNECTOR)

(a) Disconnect the central gateway ECU (network gateway ECU) connector.

*a

Front view of wire harness connector

(to Central Gateway ECU [Network Gateway ECU])

*b

Front view of DLC3

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

I160-6 (CA3H) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

I160-21 (CA3L) - I182-16 (BAT)
OK

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

NG

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 10 CAN JUNCTION CONNECTOR)

4.

CHECK FOR SHORT TO B+ IN CAN BUS WIRE (ECU, SENSOR)

(a) Reconnect all wire harness connectors.

*a

Component with harness connected

(Central Gateway ECU [Network Gateway ECU])

*b

Front view of DLC3

(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to +B is connected.

Click here

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

I160-6 (CA3H) - I182-16 (BAT)

Cable disconnected from negative (-) auxiliary battery terminal

6 kΩ or higher

I160-21 (CA3L) - I182-16 (BAT)

HINT:

  • If the resistance changes to 6 kΩ or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.
  • If the resistance does not become normal when the connector is disconnected from the ECU or sensor, check for a short to +B in the wire harness and repair or replace the wire harness or connector if necessary.
OK

REPLACE ECU OR SENSOR
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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